Rho guanine nucleotide exchange factor (RGNEF) is a prosurvival factor under stress conditions

- The expression of RGNEF is upregulated in murine spinal motor neurons following distal sciatic nerve injury
- That in response to in vitro cellular stress, RGNEF confers a significant survival benefit;
- The survival benefit of RGNEF is conferred by the NH2-terminus domain which harbours a leucine-rich region; and,
- In response to a stress, RGNEF partitions to Staufen1 positive granules but not TIA-1-positive stress granules.

Rho guanine nucleotide exchange factor (RGNEF) is a 190 kDa RNA binding protein (RBP) that also contains a Dbl/PH domain capable of RhoA activation. Consistent with a key role in the pathogenesis of amyotrophic lateral sclerosis (ALS), RGNEF forms pathological neuronal cytoplasmic inclusions in degenerating spinal motor neurons. To further understand the role of RGNEF in the stress response, we first observed that the expression of RGNEF is upregulated in murine spinal motor neurons following distal sciatic nerve injury. Secondly, in response to in vitro cellular stress (500 μM sodium arsenite for 1 h; or 400 mM sorbitol 1 hour exposure; as an oxidative or osmotic stress, respectively), we observed a significant survival benefit in RGNEF-transfected HEK293T cells. Using deletion constructs, we found that the NH2-terminus domain is essential for this protective effect. Interestingly, we observed that under stress conditions RGNEF associates with Staufen1 positive granules but not TIA-1-positive stress granules. These findings support the hypothesis that RGNEF plays a critical role both in RNA homeostasis and in the response to cell stress.